anahim hotspot ascension island asthenosphere azores big bang british columbia canada canary islands convection copper coral sea cretaceous diapir digital object identifier eclogite elevation flood basalt geochemistry geoid geophysics gold hallasan hawaii hawaiian-emperor seamount chain hotspot iceland plume igneous rock indian plate isotope jeju-do karmutsen formation large igneous province lava lamp lithosphere magma metasomatism nickel norilsk oceanic plateau osmium p-wave pge peridotite plate tectonics queensland seismic tomography seismology siberian traps structure of the earth supercontinent volcano